The present invention relates to roll cleaning systems for metal working machinery and, more particularly, to systems for cleaning the work and backup rolls of tension levelers.
In a tension leveling operation, strip metal is cold worked by passing it about small radius rolls positioned to provide up and down bends with the strip under tension, which results in uniform elongation of strip fibers beyond the yield point of the metal. The result of this uniform elongation is to provide a consistent plastic deformation across the entire width of the strip. This introduces a homogenous stress pattern that avoids problems of distortion of the strip inherent in the rolling process which result from variations in thickness of the strip across its width.
In order to provide sufficient elongation in a relatively short run, it is desirable to minimize the diameter of the work rolls around which the sheet material is passed under tension, which results in greater elongation per pass. Due to the stresses involved, it is necessary to support such small-diameter work rolls on larger diameter backup rolls in order to prevent deflection of the work roll. A problem inherent in tension leveling processes is that the work and backup rolls pick up contaminants which collect on these rolls and may adversely affect the desired quality and speed of the leveling process.
This problem is especially pronounced when strip aluminum is tension leveled. Strip aluminum contains particles of aluminum oxide which are extremely hard and abrasive. Such particles tend to collect on the work and backup rolls and cause brinelling of the backup roll, vibrations of the sheet, and a degradation in the quality of the leveled strip aluminum.
Efforts have been made in other areas to remove particulates accumulated on work rolls. For example, Kirschner U.S. Pat. No. 3,379,044 discloses a rolling mill in which the work rolls contact rotary brushes and scrapers, purportedly to remove collected particles. However, a potential disadvantage with such systems is that the particles removed are not contained; rather, they are merely removed from the work roll and held briefly, if at all, on the rotary brush, which may drop them in the surrounding area. This debris may create a hazard and increase the cost of operation due to frequent clean up activity.
Accordingly, there is a need for a roll cleaning system which affectively removes contaminants from work rolls and backup rolls of tension levelers and retains the removed material for efficient disposal.